Citizen Chronograph 8100A 4-900031TA Challenge Timer


This must be one of the most beautiful Citizen ever made. And that is not an easy thing to declare, but I think in this case, it is most likely true. Just take a look at the way the light is dancing on the hour markers, the blue metallic finish, black case… the color of the hands… poetry! This is the Citizen Chronograph Challenge Timer 4-900031TA.

Citizen had three chronograph movements. The first one is a manual wind, found in Citizen Recordmaster – HERE, and two automatic calibres, based on the same main design. The watch presented here is powered by 8100A.

Citizen vintage chronograph 8100A

The case is black coated and has a stainless steel case back and bezel. The chronograph pushers and the crown are also SS. The bracelet is a very interesting combination of black coated metal parts and black leather. Because it is such an old watch, most of the leather parts on these bracelets are, unfortunately, ruined. I am glad I found this NOS example with intact parts. (I have one more bracelet like this in great need of new leather parts, so if anyone interested in that, let me know.) About the caseback – here you can see the way it was sealed with stickers the day it was made –  “passed JWCII” The JWCII was used since 1954 and lasted up to 1991. It was made for a specific reason: to ensure quality control. They were applied in factories producing horological and other technological products. JWCII sticker (initially placed on watches where QC was an important step of manufacture) was later-on seen on Japanese cameras and lenses and a few electronic devices.

The movement is the automatic fly-back, 23 jewls, calibre 8100A with hand winding capability. It was produced by Citizen starting from 1972, just as 8110A. This watch was made in 1973, It is a vertical clutch chronograph (beating at 28.800 bph) with column wheel and fly back function. It also features a day and date indicator. The fly back function means that you can reset the chronograph while in motion and it will start again without needing to go the entire process of pressing stop-reset-start. So, one push can do all of this. Of course that if you want to stop it you can go the classic stop-reset way. A particularity for this movement is that when you want to change the day you should pull the crown to second position (for changing the date) and push and release the reset (5 o’clock) button. It is 27 mm wide and 5,8mm high, (1mm less than 8110A). The column wheel/vertical clutch design of the movement advices to leave the chronograph running for most of the time (this way you can also see the beautiful sweeping central second hand in movement), but from time to time it should be stopped. This is a chronograph that needs to be used. It is not made for design purpose but for timing.

And… now let’s tall about the way it looks. 🙂 The awesome dial is blue, with a sun burst effect, metallic and reflects the light in various ways, making it sparkle to life in direct sun light. In the shade it becomes darker and sometimes even close to black. The hour markers are applied and have orange accents. The hands are orange too, for perfect complementary color contrast (blue – orange). On the outer part of the dial is the white Tachymeter scale.

Beautiful watch, wonderful movement. Great to have, look at and a joy to wear.

Read more about Citizen chronographs on the dedicated page HERE.

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6 thoughts on “Citizen Chronograph 8100A 4-900031TA Challenge Timer

  1. Hello,
    I would like to know, if the crystal on the watch is mineral (glass) or plastic ?
    Do you have any spare one to sell (could also be aftermarket) ?
    I would also need one chrono pusher…
    Thanks
    Andrej

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    • Hello Andrej! The crystal is mineral glass but I don’t have one for sale and no pusher. You can ask about any watchmaker to fit an aftermarket crystal and it will be ok. With the pusher is a different story. Good luck with the restoration! 😉

      Like

  2. The case is black coated and has a stainless steel case back and bezel. The chronograph pushers and the crown are also SS. The bracelet is a very interesting combination of black coated metal parts and black leather. Because it is such an old watch, most of the leather parts on these bracelets are, unfortunately, ruined. I am glad I found this NOS example with intact parts. (I have one more bracelet like this in great need of new leather parts, so if anyone interested in that, let me know.) You still have this bracelet let me know please

    Like

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